| 摘要 |
A shaft (40) subject to torque about its axis (A-A) has an axial bore (42). A region (44) of the shaft (40) has a stored magnetisation, the region (44) being permanently magnetised with circumferential magnetisation about the axis (A-A) or an annulus of longitudinal magnetisation which is preferred. The stored magnetisation emanates a torque-dependent field into the bore (42). A magnetic field sensor arrangement (50) is positioned in the bore to produce a torque-dependent signal. The disclosure discusses the relationship between the radial depth (tm) of the permanent magnetisation in region (44) relative to the shaft wall thickness (t). Magnetic sensor placements include axial (52, 54) or offset arrangements of pairs of sensors (52a,b, 54,b). Dependent on the nature of the field to be sensed, sensors (5) may be oriented axially, radially or tagentially with respect to the axis (A-A).
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